Abstract Oxidative stress (OS) has been implicated in the pathogenesis of autoimmune diseases (ADs), including systemic lupus erythematosus (SLE), and a large number of environmental chemicals are known to cause OS. Our long-term goal is to elucidate the role of OS in the development of ADs that are induced by environmental chemicals, and use this information to design preventive or therapeutic strategies. Trichloroethene (TCE) has been implicated in causing ADs, including SLE-like diseases in humans. Previously, we have established an association between TCE-mediated OS and autoimmune response/SLE. This competitive continuation application is based on the premise that TCE exposure affects diverse OS-responsive pathways to lead to a pathogenic response. We hypothesize that TCE-induced oxidative stress causes impairment in PARP-1 and Nrf-2 expression, leading to a harmful inflammatory/autoimmune response. Furthermore, lipid-derived reactive aldehydes (LDRAs) cause structural modifications to endogenous proteins, resulting in the formation of neoantigens which, via lymphocyte activation, contribute to ADs. To test our hypothesis, the following specific aims are proposed: Aim 1 will define the role of PARP-1 activation in TCE-mediated autoimmunity/SLE and will test the hypothesis that TCE-induced activation of PARP-1 leads to a pro-inflammatory response and confers higher susceptibility for SLE/autoimmunity. Studies in this aim will establish a clear link between PARP-1 activation and TCE-mediated autoimmunity/SLE, determine that modulation of PARP-1 abrogates TCE- mediated autoimmune response, and examine PARP-1's potential to act as a coactivator of NF-kB-mediated transcription of pro-inflammatory mediators/cytokines. Aim 2 will determine that impaired Nrf2 expression plays a critical role in the pathogenesis of TCE-mediated SLE, and will test the hypothesis that reduced expression of Nrf2 exacerbates the development of TCE-mediated lupus nephritis. Nrf2 activation will likely attenuate inflammation and disease pathogenesis. Studies in this aim will establish that absence of Nrf2 exacerbates TCE-mediated autoimmune response, and also determine that antioxidant sulforaphane (SFN) ameliorates TCE-mediated SLE by upregulating Nrf2. Aim 3 will elucidate that lipid-derived reactive aldehydes (LDRAs) contribute to TCE-mediated SLE, and will test the hypothesis that LDRA modification of endogenous proteins results in the formation of neo-antigens, which by activating lymphocytes can elicit an autoimmune response. We will determine that LDRA-protein adducts aggravate T cell proliferation, especially Th17 cells, and induce inflammatory cytokines. Furthermore, we will characterize LDRA-protein adducts (proteomic approaches) and determine their autoimmune potential. Our studies will firmly establish a role for OS in the induction and/or exacerbation of autoimmunity/SLE, will delineate novel mechanisms of pathogenesis, and will serve as a stepping stone to translational strategies to prevent autoimmune responses to TCE and other chemicals/drugs known to cause toxicity via OS.